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From: squishy@casbah.acns.nwu.edu (Shishin Yamada)
Newsgroups: comp.sys.atari.8bit
Subject: Re: 65C02?
Message-ID: <1991Mar6.190420.20620@casbah.acns.nwu.edu>
Date: 6 Mar 91 19:04:20 GMT
References: <1991Mar5.110713.24023@cs.city.ac.uk> <19374@brahms.udel.edu>
Organization: Northwestern University
Lines: 41


	Sorry, just thought I'd add my two cents worth... The striaght
drop-in replacement of the 6502 by a 65C02 would ALMOST SURELY not work.

	It has a lot to do with the logic voltages of TTL compatable (6502
is an MOS device from Motorola and uses TTL compatable logic voltages), and
CMOS devices. The voltages for logic 0's and 1's differ between the two
chip technologies (CMOS has lower voltages). It is however interesting to
note that the 65C02 used in the 130xe series is FASTER than the standard
6502 running at 1.79MHz (incidentally, if you're wondering why 1.79MHz, it
is because it is an even factor of the TV color-burst frequency... 3.58MHz.
Makes video interfacing easier and it's cheaper to find a color-burst
crystal). Typically, CMOS is the slowest familly of Logic, so this must be
a variation, like HC (High Speed CMOS). While MOS technology is similar,
every MOS chip I've seen from Motorola is directly TTL compatable, and we
are taught to think of them in terms of a TTL type family of logic chips.

	In this case, even if the 65C02 added an internal line-driver
(sometimes done to correct for the difference in logic voltages), often the
CMOS version has a different pin-out than the TTL version. Also, the 65C02
adds some new instructions to supplement the standard 6502 code to make
things a little faster.

	To make a long story short, you are probably better off purchasing
a 130xe for cheap, than to fiddle with an old 800.

PS: I was a 800 user since 1980, then a 130xe user from 1985-1988. Now I am
a happy Mac II user. However, there's nothing like an Atari for easy
hardware interfacing. I wish I could show you the robot interface I once
built (at the cost of a fried 130xe!)
 
=====================================================
Shishin "Squish" Yamada                    |\/\/\/|
 squishy@casbah.acns.nwu.edu  /---------\  |      |
 Northwestern University      | Yo      |  (o)(o) |
 Electrical Engineering       |  Dudes! \  ( <    )
 Class of 1991                \__________\ |___/  |
                                             \    |
  "Life sucks, but Death swallows!"          /    \
                                            /______\
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